How to *officially* figure out if you’re lactose- or gluten-intolerant

If you suspect you’re eating something that doesn’t agree with you—and it happens on the reg—chances are your mind jumps straight to the milk in your coffee or your sandwich on whole wheat bread. After all, as far as food sensitivities go, lactose and gluten are two of the more widely maligned culprits.

The trouble is, the symptoms of lactose intolerance and non-celiac gluten sensitivity (or NCGS) can often overlap, making it hard to figure out which one—if either—is causing your digestive distress. “Gastrointestinal issues, such as bloating, gas, problems with bowel movements, abdominal pain, fatigue, and headaches are common with both,” explains registered dietitian Maxine C. Yeung, MS, RD, CPT, CWC, founder of The Wellness Whisk.

There are a few ways you can get to the bottom of what’s bugging you, though. Whether you want to go the blood-test route or choose to play detective via your diet, experts agree that there’s no need to rely on wild guesses in an attempt to feel better. I mean, wouldn’t it be great to discover that you don’t really have to ditch pasta or ice cream in the end?

Here’s how to tell if you might have lactose intolerance or gluten sensitivity. (Or neither. Or both.)

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The difference between lactose intolerance and gluten sensitivity

Even though symptoms can be similar, lactose intolerance and NCGS are quite different.

“Lactose intolerance is fairly straightforward—it occurs when an individual no longer produces the lactase enzyme in sufficient quantities,” says integrative and functional dietitian and nutritionist Ryan Whitcomb, MS, RD, CLT, owner of GUT RXN Nutrition. (Many people don’t once childhood ends or they’ve quit dairy for an extended amount of time.) “Lactase is responsible for breaking down lactose, the natural sugar found in dairy products like milk. Since the body is not able to break this sugar down in the small intestine, where it’s supposed to be digested, it moves into the large intestine.” Here, it produces gas, which causes those unpleasant GI symptoms.

NCGS, on the other hand, isn’t well understood. It can cause the same wide range of symptoms as celiac disease, which, in addition to tummy trouble, can include things like brain fog, rashes, and joint pain. However, celiac disease is an autoimmune condition that causes actual damage to the small intestine, whereas NCGS doesn’t. “For some reason, people with NCGS cannot tolerate gluten, but we don’t currently know why,” says Whitcomb. What is known is that people with NCGS should follow a gluten-free diet.
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How to diagnose food intolerances the high-tech way…

Depending on your health pro’s MO, he or she may choose to investigate your potential food intolerances with testing. “The best test for lactose intolerance is a breath test, of which there are two types: the lactose hydrogen breath test and the hydrogen/methane breath test,” says Whitcomb. These tests can measure how much gas is being produced after the consumption of dairy, and Whitcomb says the latter is more accurate.

NCGS is much more difficult to test for. First, it’s important to make sure you don’t actually have celiac disease, notes Amy Gorin, MS, RDN, owner of Amy Gorin Nutrition. “There are blood tests to diagnose celiac disease, and for these tests to be accurate, they must be done while you are consuming a gluten-containing diet,” she says. (So don’t cut out the croissants just yet.) “A biopsy of the small intestine can confirm positive blood-test results.”

It’s worth noting that celiac testing results aren’t always black and white. But if celiac disease and other problems—like a wheat allergy, SIBO, or other intolerances like lactose—have been ruled out, NCGS may be your issue. The only way to know for sure is to see whether you feel better without gluten in your diet.

Whitcomb’s preferred method to diagnosing food sensitivities in his practice, though, is the Mediator Release blood test (or MRT). It looks at up to 170 foods and chemicals, and while it doesn’t test for gluten intolerance directly, it tests gluten-containing foods like wheat, barley, and rye.

Want to know more about gluten? Check out this video for the full DL:

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…And the DIY route to decoding your symptoms

The problem with medical tests? They aren’t always 100 percent accurate, and they can also be very costly. Another option is a good old-fashioned elimination diet—basically, that means you just stop eating iffy foods and see how you feel.

“If you strongly suspect your symptoms may be related to either lactose or gluten, then eliminating the individual categories may be okay,” says Yeung. (That is, just removing gluten and/or lactose.) “If you’re unable to see patterns in the foods you eat and your symptoms, then I’d recommend a full elimination diet,” she says. While elimination diets vary, they often rule out foods like dairy, gluten/wheat, eggs, soy, nightshades, and more.

Unfortunately, this is probably the most time-consuming and restrictive plan of action. But if you’re diving into the challenge, here’s how it usually goes down. “Typically you begin by eliminating all sources that may be causing adverse effects for at least one to two weeks,” says Yeung. “After the initial phase, you begin reintroducing foods from one category at a time while continuing to eliminate the other categories.”

There’s no correct order in which to reintroduce foods—the most important thing is that you test only one food at a time. For example, when you’re reintroducing dairy, you might start with a small amount of milk one day, monitor symptoms in a journal, then try a little more the next day. “If this food is a problem food, you will likely experience symptoms,” says Yeung. Even if you don’t react to it, Yeung recommends repeating the process twice for each food group for max accuracy.

You might find that you feel more tired with gluten in your diet, or that foods made with milk mess with your bathroom habits. Or maybe, you find another result that’s completely unexpected. Yes, the quest to uncover food sensitivities can be tough—but if it comes with a calmer gut or more energy, isn’t that totally worth it?